OF THE ASBESTINE EARTH. 197 



Exi>. 41. and 42. Whether tried by fire in 

 the crucible, or by the blow-pipe, it difcovcrs the 

 uiual qualities of ichorL 



Exr. 43. liy analyfis, the centenary produ- 

 ces of terra ponderoia, o; aerated chalk, 9,3; 

 aerated magncfia, 20; clay, 2.7; filiccous earth 

 64 ; and calcined iron, 4, 



Having proceeded thus far, it may perhaps 

 be not altogether u fold's to defcribc more par- 

 ticularly the method by which the different a- 

 nalyfcs were conduded. The it ones intended 

 for examination being firll reduced to the fined 

 powder, and exactly weighed, were thoroughly 

 mixed with fixed vegetable alkali and powder- 

 ed charcoal, and then ignited for two hours in 

 a covered crucible ; at which period the cover 

 being removed, they wrre calcined until the 

 charcoal was completely dephlogiilicatcd. The 

 lleatites alone was not expofed to this proccfs, 

 as its folubility was fullicicntly proved by other 

 experiments The alkali employed was the 

 pure fait of tartar. In all the trials, both the 

 quantity and quality of the charcoal being the 

 fame, there was no realon to apprehend the ad- 

 mixture of any foreign fubflancc. A centenary 

 of this coal yielded no more than z| ofafiies. 

 After the calcination, the powders became more 

 or lets blue or green, and communicated dired- 

 Jy to a fmall quantity of water poured upon 

 N 3 them 



